Alkaline photographic developer concentrate

ABSTRACT

A substantially clear aqueous alkaline solution concentrate adaptable for use as a component of a photographic color developer kit, the solution including, as a buffer, carbonate, and further including sulfoxylate.

United States Patent 1191 Fisch et al.

[451 Feb. 5, 1974 1 ALKALINE PHOTOGRAPHIC DEVELOPER CONCENTRATE [75] Inventors: Richard S. Fisch; Norman Newman,

both of St. Paul, Minn.

[73] Assignee: Minnesota Mining & Manufacturing Company, St. Paul, Minn.

[22] Filed: Sept. 24, 1971 [21] Appl; No.: 183,673

[52] U.S. Cl 96/66.1, 96/66.4, 96/66 R [51] Int. Cl G036 5/30 [58] Field of Search 96/66, 66.1, 66.4, 55

[56] References Cited UNITED STATES PATENTS 2,727,062 12/1955 Tulagin ..96/66.4

Primary Examiner-J. Travis Brown Assistant ExaminerM. F. Kelley Attorney, Agent, or Firm-Kinney, Alexander, Sell, Steldt & Delahunt 57 ABSTRACT A substantially clear aqueous alkaline solution concentrate adaptable for use as a component of a photographic color developer kit, the solution including, as a buffer, carbonate, and further including sulfoxylate.

5 Claims, No Drawings ALKALINE PHOTOGRAPHIC DEVELOPER CONCENTRATE This invention relates to photographic color developer concentrate kits, and more particularly to aqueous alkaline solution concentrates for use in such kits.

Chemicals which are utilized to color-develop exposed silver halide materials are generally sold in the trade in concentrated form so that, by simple dilution with water, the ultimate usermay obtain a photographic color developer working solution. To avoid the tendency of certain ingredients of photographic color developer concentrates to react with one another, it is often desirable to provide various of these ingredients in separate packages. For example, a concentrated acidic aqueous solution of a photographic color devel-' oping agent may be placed in one package ofa kit, and

a concentrated aqueous alkaline solution may be included in a second package thereof. The photographic color developer working solution may then be prepared simply by combining the packaged ingredients and diluting the same with water.

The aqueous alkaline solution concentrate which is a component of a color developer concentrate kit commonly includes an alkaline buffering agent (for example', a borate, carbonate or phosphate salt) and an antioxidant for the working developer to be prepared from the kit, the antioxidant usually being a sulfite salt such as sodium sulfite. Borate buffers, although yielding satisfactory results, are quite expensive. On the other hand, carbonate buffers are much less expensive, and significant cost savings can be achieved by their use. When a carbonate buffering agent is used in an aqueous alkaline solution concentrate together with a sulfite antioxidant, however, a precipitate forms. Although the precipitate can be redissolved upon adequate dilution of the alkaline solution concentrate with water during preparation of the working developer, excessive periods of time are required to completely dissolve the precipitate. It is desirable, of course, that one be able to quickly prepare a working developer solution simply by opening the packaged chemical concentrates, and diluting the same with water. The necessity of dissolving a precipitate in a developer working solution is time consuming, inconvenient, and desirably should be avoided. Attempts to utilize a working developer before complete dissolution therein f the various components thereof may cause quality control problems and may result in inconsistent processing characteristics.

It is an object of the present invention to provide a substantially clear, storage-stable aqueous alkaline solution concentratewhich is carbonate-buffered andwhich is adaptable for use as a component of .a photographic color development kit.

Briefly, we have found that a substantially clear aqueous alkaline solution concentrate buffered with carbonate results when sulfoxylateis employed as the antioxidant thereof. Accordingly, in one embodiment the in vention relates to a substantially clear aqueous alkaline solution concentrate adaptable for use as a component of a photographic color developer kit, the solution containing at least 1.85 molar equivalents per liter of carbonate, and sufficient molar equivalents of sulfoxylate to provide a molar ratio of sulfoxylate to carbonate of from about 0.01/1 to about 0.25/1. In a second embodiment, the invention relates to an improvement in a photographic color developer kit which includes a photographic color developer solution concentrate and an aqueous alkaline solution concentrate. In the improvement, the aqueous alkaline solution concentrate contains at least 1.85 molar equivalents of carbonate per liter and further includes sulfoxylate in sufficient quantity to provide a molar ratio of sulfoxylate to carbonate of from 0.01/1 to about 0.25/1. Yet another embodiment of the invention relates to a method for the preparation of a photographic color developer solution which comprises combining, in aqueous solution, an aqueous p-phenylenediamine color developer concentrate and a substantially clear aqueous alkaline solution concentrate which includes at least 1.85 molar equivalents per liter of carbonate and sufficient molar equivalents of sulfoxylate to provide a molar ratio of sulfoxylate to carbonate in said alkaline solution of from about 0.01/1 to about 0.25/1. By substantially clear solution" as used herein is meant a solution which visually exhibits no significant turbidity when viewed under normal indoor lighting conditions. The photographic developer working solutions referred to herein, of course, include developer replenisher solutions.

The use of sulfoxylate as the primary or sole antioxidant in the aqueous alkaline solution concentrates of the invention now permits carbonate buffers to be utilized therein and avoids the problem previously associated with the formation of a precipitate. Although sodium formaldehyde sulfoxylate has previously been utilized in working strength developers (British Patent 462,140), it is surprising that the use of sulfoxylate as an antioxidant in'the concentrates of the present invention permits precipitationto be avoided and thus permits the aqueous alkaline solution concentrates of the invention to be rapidly dissolved during preparation of a working color developer solution.

The concentration of carbonate in the aqueous alkaline concentrates of the present invention must be at least 1.85 molar, and is limited only by the solubility of carbonate in the solution. By carbonate as used herein, reference is made to water-soluble carbonate salts such as sodium, potassium and ammonium carbonate, i.e., salts which are capable of liberating carbonate ion when dissolved in water. A carbonate concentration of from about 3 to about 6 molar is preferred. I

The concentration of sulfoxylate in the aqueous alkaline solution concentrates of the present invention is chosen so as to provide a molar ratio of sulfoxylate to carbonate of from about 0.01 /1 to about 0.25/1, and preferably from about 0.03/1 to 0.15/1. By sulfoxylate as used herein, reference is made to sulfoxylate salts such as sodium formaldehyde sulfoxylate, i.e., salts which are capable of liberating the sulfoxylate ion when dissolved in water.

The aqueous alkaline solution concentrates of the invention may, of course, contain various other additives such as developer restrainers (e.g., bromide ion), and anti-foggant (e.g., benzotriazole), sequestering agents, for example, ethylenediamine tetraacetic acid, amino polyalkyl carboxylic acids and derivatives thereof, etc. In its preferred embodiment, the aqueous alkaline solution concentrate of the present invention contains a small, non-precipitating quantity of a sulfite ion precursor such as sodium sulfite. By non-precipitating is meant that the sulfite ion precursor is employed in an amount which does not cause precipitation of any of the components of the solution.

As mentioned above, a working color developer solution may be prepared by combining the aqueous alkaline solution concentrate of the invention with another solution concentrate which includes a photographic color developing agent, and diluting the mixture with water to a predetermined concentration. The photographic color developing agent of choice is a p-phenylene-diamine developing agent, and this agent is normally dissolved in water to form an aqueous, acidic solution concentrate which may represent one of the components of a photographic color developer kit. As known in the art, a photographic color developer agent is a compound which is capable of reducing silver halide to silver. The developing agent is concurrently oxidized, and the oxidation product of the developer is capable of reacting (coupling) with a photographic color coupler to form a dye. The photographic color developer solution concentrate with which the solution of the present invention is combined to form, upon dilution, a working color developer may contain various other components such as, for example, oxidation inhibitors (e.g., sulfite), antifoggants (e.g., benzotriazole), development restrainers (e.g., bromide ion), auxiliary black and white developing agents, and the like.

Developer kits which include the aqueous alkaline solutionconcentrate of the present invention will normally be sold in unitary kit form, each kit containing two ormore packages. The'various packages will be chosen by size and shape to accommodate the various ingredients and concentrations of ingredients for each package, and will be further chosen so as to result in a total package of minimum size and weight to minimize shipping and storage costs. Accordingly, it may be desirable in some instances to place a given chemical composition (e.g., sulfite) in more than one package to conserve space.

The invention may be more easily understood by reference to the following illustrative, non-limiting example.

A 3-package developer kit was prepared, the composition of each of the packages being as follows:

Potassium carbonate 40. 3

g. Sodium formaldehyde sulfoxylate 2.3 g. Potassium bromide 0.16 g. Ethylenediamine tetraacetic acid l.6 g. Water 57.5 ml.

It was immediately noted that a precipitate formed in package C (sulfite-containing).Package C' (sulfoxylate-containing) was substantially clear.

Working developer solutions were prepared from both of the kits listed above by combining the ingredients of the various packages of each kit, and diluting the same with water to a total volume of 1,000 milliliters. The working developer solution formed from the kit which contained package C was clear whereas the working developer solution formed from the kit containing package C (sulfite-containing) was initially turbid due to the presence of the precipitate, and considerable time was expended in stirring .the solution to effect dissolution of the precipitate. Both, working solutions were exposed to air for 12 hours, but no stability differences were noted, nor were differences noted in the ability of the two solutions to develop silver halide color film.

What is claimed is:

l. A substantially clear aqueous alkaline solution concentrate adaptable for use as a component of a photographic color developer kit, said solution containing at least "1.85 molar equivalents of carbonate liberated from the group selected from potassium, sodium and ammonium carbonate per liter and sufficient molar equivalents of sodium formaldehyde sufloxylate to provide a molar ratio of sulfoxylate to carbonate of from about 0.01-0.25 to l.

2. The solution of claim 1 which includes an amount of sulfite ion precursor which does not cause precipitation of any of the components of the solution.

3. The solution of claim 1 wherein said carbonate is potassium carbonate.

4. The solution of claim 1 wherein said carbonate is present in a concentration from about 3 to about 6 molar equivalents per liter.

5. A method for the preparation of a photographic color developer solution which comprises combining, in aqueous solution, an aqueous p-phenylenediamine 5 color developer concentrate and a substantially clear aqueous alkaline solution concentrate which includes at least 1.85 molar equivalents of carbonate liberated from the group selected from potassium, sodium and ammonium carbonate per liter and sufficient molar equivalents sodium formaldehyde of sulfoxylate to provide a molar ratio of sulfoxylate to carbonate in said alkaline solution of from about 0.0l0.25 to l.

i I! i l i UNITED STATES PATENT omen CERTIFICATE OF CORRECTION I Patent No. 3,79 ,3 Dated February 5, 197

Venn-('8) Richard S. Fisch and Norman Newma n It is certified that error appears in the shove-identified patent and that said Letters Patent are hereby corrected as shown below: Column line 56, "1O sesquisulfate" should read -sesquisulfate-. v 7

Column 4, line 59, "equivalents sodium formaldehyde of sulfoxylate" should read --equivalents of'sodiu m formaldehyde sulfoxylate--. j I

Signed a nd seeledfihis 19th' -daylof November 1974.

(SEAL) Attest:

MCCQY M. GIBSON 'JR. C MARSHALL DANN Attesting- Officer Commissioner of Patents USCOMM-DC GONG-P69 u s mwnrmzm numncovr c: nu o-su-au. 

2. The solution of claim 1 which includes an amount of sulfite ion precursor which does not cause precipitation of any of the components of the solution.
 3. The solution of claim 1 wherein said carbonate is potassium carbonate.
 4. The solution of claim 1 wherein said carbonate is present in a concentration from about 3 to about 6 molar equivalents per liter.
 5. A method for the preparation of a photographic color developer solution which comprises combining, in aqueous solution, an aqueous p-phenylenediamine color developer concentrate and a substantially clear aqueous alkaline solution concentrate which includes at least 1.85 molar equivalents of carbonate liberated from the group selected from potassium, sodium and ammonium carbonate per liter and sufficient molar equivalents sodium formaldehyde of sulfoxylate to provide a molar ratio of sulfoxylate to carbonate in said alkaline solution of from about 0.01-0.25 to
 1. 